Category Filter only filters object detection model results, not ground truth

[PaulHax]

Thats strange because if you

1. "Apply" category filter with cow as a item, no images are selected
2. Select the zebra and wildabeast image. Detection model annotates the wildabeast as cow.
3. "Apply" category filter with cow as a item -> Surprise! Zebra/Wildabeast image is selected.
4. Deselect Zebra/Wildabeast
5. "Apply" category filter with cow as a item -> Surprise: no images are selected (but Zebra/Wildabeast was selected before!)

Strange that we select images based on if they are currently selected. If thats what we want, then category tags need to be updated on each image set selection.

Relevent code:
https://github.com/Kitware/nrtk-explorer/blob/main/src/nrtk_explorer/app/core.py#L146-L149

[vicentebolea]

Thanks for pointing this out, we probably want to filter ground truth.